1. Field of the Invention
The present invention relates to semiconductor memory devices. Further, the present invention relates to semiconductor devices on which semiconductor memory devices are mounted.
2. Description of the Related Art
Recently, an individual-recognition technology has attracted attention. In the individual-recognition technology, an individual identification number (ID) is given to each individual object so that information such as a history of the object can be identified and used for production, management, and the like. In particular, an individual-recognition technology in which semiconductor devices which are capable of transmitting and receiving data without contact are used has been developed and starts to be introduced into companies, markets, and the like. Such a semiconductor device is referred to as a radio frequency identification (RFID) tag, an RF tag, an ID tag, an integrated circuit (IC) tag, an IC chip, a wireless tag, a wireless chip, or the like.
By mounting a memory device (hereinafter, also referred to as a memory or a memory circuit in this specification) on such a semiconductor device, a semiconductor device with higher function (hereinafter, also referred to as a semiconductor memory device in this specification) can be realized. Among the memory devices mounted on the semiconductor memory devices, a memory having a plurality of memory cells which are writable only once, which is one type of a nonvolatile memory, is preferable from a security standpoint because tampering with the data is not easy. Such a memory is referred to as a one-time programmable memory (hereinafter, also referred to as an OTP memory or simply an OTP in this specification).
As one type of an OTP memory, an antifuse memory (hereinafter, also referred to as a silicide memory in this specification) has been proposed. In an antifuse memory, one of electrodes is formed using metal and an antifuse becomes conductive by a silicide reaction of amorphous silicon with the metal (for example, see Patent Document 1).
In addition, a circuit has been proposed in which a capacitor for supplying electric power in writing (hereinafter, referred to as an assist capacitor in this specification) is provided in parallel with a memory element in a memory cell of an OTP memory (for example, see Patent Document 2). In particular, in a silicide memory, a high writing yield can be achieved by providing an assist capacitor.